Question

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NEED CORRECT ANSWER.

Answer 1

Principal = Rs 640

Principal + investment = Rs 774.40

Number of years = 2

Find the interest rate

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Formula : A = P(1 + r/100)²

Find r:

774.40 = 640(1 + r/100)²

Divide both sides by 640:

744.40 ÷ 640 = (1 + r/100)²

1.21 = (1 + r/100)²

Switch sides:

(1 + r/100)² = 1.21

Square root both sides:

1 + r/100 = √1.21

1 + r/100 = 1.1

Subtract 1 from both sides:

r/100 = 1.1 - 1

r/100 = 0.1

Multiply both sides by 100:

r = 10%

Answer: The interest rate is 10%